A conventional gas turbine engine includes various rotor blades in the fan, compressor, and turbine sections thereof, which are removably mounted to respective rotor discs. Each of the rotor blades includes a blade root at the radially inner end thereof. Each of the blade roots conventionally includes one or more pairs of lobes which can axially slide into and be retained in one of a plurality of axially extending attachment slots in the periphery of the rotor disc. In high pressure turbine rotor assemblies, blade fixing attachments with turbine discs have been conventionally oriented in a direction substantially parallel to the engine axis. The constant quest to improve the efficiency of engines as a whole, and in the turbine area in particular, have lead to changes in the geometry of the gas path, resulting in an increase in the stresses on blades and blade firtrees, and an increasing need for a blade cooling flow provided at high pressure ratios. It has been found that in the conventional blade fixing attachment configurations, significant pressure loss of cooling air flow occurs through Tangential On Board Ingestion (TOBI) systems, especially at the point of blade entry.
Accordingly, there is a need to provide an improved blade root retaining system for turbine assemblies of gas turbine engines in order to meet the demanding requirements of various aspects of high efficiency gas turbine engines.